Circuit breaker with low short circuit magnetic tripping means

ABSTRACT

AN ELECTRICAL CIRCUIT INTERRUPTER HAS A MOVABLE CONTACT CARRIED BY A CONTACT OPERATING MEMBER FOR MOVEMENT RELATIVE TO STATIONARY CONTACTS BETWEEN CLOSED AND OPEN CIRCUIT POSITIONS. OPERATING MEANS WILL MOVE THE OPERATING MEMBER FROM CLOSED TO OPEN CIRCUIT POSITION UPON RELEASE OF LATCHING MEANS ENGAGED THEREWITH. THE CONTACT OPERATING MEMBER CARRIES AN ARMATURE WHICH IS SUBJECT TO THE MAGNETIC ATTRACTION OF A SOLENOID COIL SO AS TO BE MOVABLE TO OPEN CIRCUIT POSITION UPON PASSAGE OF A SHORT CIRCUIT CURRENT OF PREDETERMINED MAGNITUDE THERETHROUGH. A SECOND ARMATURE ALSO ACTED UPON BY THE MAGNETIC FIELD OF THE SOLENOID COIL IS MOVABLE INTO A CIRCUIT OPENING POSITION UPON PASSAGE THROUGH THE SOLENOID COIL OF A LESSER SHORT CIRCUIT CURRENT AND ACTS UPON THE LATCHING MEANS DURING SUCH MOVEMENT TO RELEASE THE OPERATING MEANS FOR AUTOMATIC OPERATION THEREOF.

United States Patent [72] inventor Eldon B. Heft West Hartford, Conn. 2|Appl, No. 14,453 [22] Filed Feb. 26, 1970 [45] Patented June 28, 197173] Assignee General Electric Company 54] CIRCUIT BREAKER WITH LOW SHORTCIRCUIT MAGNETIC TRIPPING MEANS 14 Claims, 3 Drawing Figs. [52] US. Cl335/16 [51] Int. Cl 11011! 77/10 [50] Field of Search... 335/16, 265,I74, 259 [56] References Cited UNITED STATES PATENTS 1,404,910 l/l922Thompson 335/259 2,686,278 8/1954 Baston.... 335/265 3,488,609 1/1970Stoke s..' 335/16 Primary ExaminerHarold Broome Attorneys-Robert S.Smith, Robert T. Casey, D. M. Schiller,

Frank L. Neuhauser, Oscar B. Waddell and Joseph B. Forman the magneticfield of the solenoid coil is movable into a circuit opening positionupon passage through the solenoid coil of a lesser short circuit currentand acts upon the latching means during such movement to release theoperating means for automatic operation thereof.

Patented June 28, 1971 [7 OFF F'IG.1

IN VEN 70/? E4 mm B. Herr 4 TWO/MIL Y CIRCUIT BREAKER WITH LOW SHORTCIRCUIT MAGNETIC TRIPPING MEANS BACKGROUND OF THE INVENTION Increasinguse of electrical power has produced requirements for power supplysystems of ever increasing capacity and a concurrent requirement forcircuit breakers capable of interrupting the high circuit currents whichcan occur in such power systems. Because of the tendency for arcing insuch circuit breakers, there has been continuing activity to developmechanisms for suppression of the arcing or for increasing the rapiditywith which the contacts may be opened.

Since most electrical circuit interrupters employ some form of automaticand manual operating mechanism for moving the contacts between closedand open circuit positions, it is highly desirable that rapid operationof the contact carrying member be effected independently of the bulk ofthe operating mechanism upon the occurrence of a high short circuitcurrent. In this manner, the inertia of the relatively massive elementsof the operating mechanism will not detract from rapid opening.

A number of arrangements for effecting a disengagable coupling oroverrideable coupling between a contact operating rod and an operatingmechanism have been disclosed. One type of mechanism which has provenadvantageous in multipole breakers is that shown in Johnson et al. U.S.Pat. No. 3,384,845 granted May 21, 1968 and assigned to the assignee ofthe present invention. A disengagable coupling between the operatingmechanism and the contact operating rod is also disclosed and claimed inGiger U.S. Pat. No. 3,495,198 issued Feb. I0, 1970 and Hurtle U.S. Pat.No. 3,483,490 issued Dec. 9, 1969, both assigned to the assignee of thepresent invention.

In the event of rapid opening of the operating rod independently of themanual operating mechanism, it is still desirable to effect operation ofthat mechanism in order to permit resetting and to indicate the trippedcondition. Moreover, in multipole breakers, it is particularly desirableto effect opening of the contacts in the other pole chambers oncetripping has occurred in one of the pole chambers.

It is an object of the present invention to provide a novel electriccircuit interrupter which is capable of rapidly opening the contactstherein independently of the manual operating mechanism and concurrentlyeffecting movement of the operating mechanism to the tripped condition.

It is also an object to provide such a circuit interrupter which may besimply and economically constructed and wherein the magnitude of theshort circuit current required for the tripping of the breaker may bepredetermined with a high degree of accuracy.

Still another object is to provide such a circuit interrupter whereinvery rapid opening of the contacts will occur by action of magneticforces generated by the short circuit current and wherein such magneticforces will act directly upon the contact operating member if the shortcircuit current is of a relatively high magnitude and will actindirectly upon occurrence of a lesser but more precisely determinableshort circuit current.

A further object is to provide such an electric circuit interrupterwhich may be readily assembled and disassembled and which is capable oflong lived operation and facile and accurate variation in the magnitudeof short circuit current required for automatic operation.

SUMMARY OF THE INVENTION It has now been found that the foregoing andrelated objects can be readily attained in an electric circuitinterrupter having a casing containing at least one stationary contactand a movable contact with a contact operating member carrying themovable contact adjacent one end thereof. Means in the casing mounts thecontact operating member for movement of the movable contact into andfrom contact with the stationary contact between closed and opencircuitpositions. Operating means in the casing is connected to theoperating member for automatically moving the contact operating memberfrom closed to open circuit position, and releasable means latches theoperating means against such automatic movement.

A first armature is supported on the contact operating member adjacentthe end thereof opposite that carrying the movable contact, and it issubject to the magnetic force of a solenoid having one end adjacentthereto. The magnetic force in the solenoid is sufficient to draw thecontact operating member into open circuit position upon passage of ashort circuit current of predetennined magnitude therethrough.

A second armature is disposed within the casing adjacent the other endof the solenoid and is attractable thereby. Means in the casing mountsthe second armature for movement from a normal position towards thesolenoid into a circuit opening position upon passage through thesolenoid of a short circuit current of predetermined magnitude, and thesecond armature acts upon the latching means during movement thereof tothe circuit opening position so as to release the operating means forautomatic operation thereof.

In its'preferred aspect, the interrupter includes adjustable biasingmeans engaged with the second armature and biasing the second annatureinto the normal position thereof. The biasing means is adjustable tovary the magnetic force required for attraction of the second armatureinto circuit opening position. The adjustable biasing means includes anadjustment lever pivotably mounted within the casing, tension springmeans connected between the second armature and the adjustment lever,and adjustable means for pivoting the adjustment lever to vary theeffective length of the tension spring means and thereby the biasingpressure exerted upon the second armature and which must be overcome bythe magnetic force generated by the solenoid.

In its usual aspect, the circuit interrupter includes a intermediatelatching member cooperating with the latch means and operable uponmovement of the second armature to circuit opening position in order torelease the releasable means for automatic operation of the operatingmeans. This intermediate latching member will normally comprise a latcharm pivotably mounted in the casing at its one end and pivotablyconnected to the second armature at its other end. The latch arm isengaged with the releasable latching means in the normal position of thesecond armature but will release the latching means upon movement of thesecond armature at the circuit opening position. The releasable meanslatching the operating means is most desirably a pivoted latch held inlatch position by engagement thereof with a portion of the intermediatelatching member.

The mounting means for the second armature will normally include a guidemember in the casing in which the second armature is slidable seated.The operating means willgenerally include a pivotable cradle and atoggle mechanism biasing the cradle for pivotable movement upon releaseof the releasable means. In addition, the operating means includes meansconnecting the toggle mechanism to the contact operating member formovement thereof into open circuit position upon pivoting of the cradle.In order to facilitate operation of the contact operating memberindependently of the operating means, the connecting means between thetoggle mechanism and the contact operating member is either releasableor over rideable upon operation of thc first armature by magnetic actionof the solenoid coil.

In a multipole circuit breaker employing the present invention, each ofthe pole chambers of the circuit breaker assembly will desirably includethe stationary contact, the movable contact, the contact operatingmember, means mounting the operating member for movement between closedand open circuit positions, the primary armature, the secondary armatureand the solenoid coil. However, the operating means for automaticmovement of the contact member from closed to open circuit position willgenerally be provided only in one of the pole chambers, conventionallythe central pole chamber. In such a multipole breaker construction, thesecond armatures of the outer poles have means thereon acting upon thelatching means of the center pole to release the operating means forautomatic operation of the central pole and thereby of the remainingpole, thus opening concurrently the contacts of each of the severalpoles upon operation of any of the poles.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a side elevational view of athree-pole electrical circuit breaker embodying the present inventionwith portions of the casing broken away to reveal internal constructionin the center pole and with certain of the elements of the outer poleillustrated in phantom line. the manual operating handle being shown infull line in the "on" or closed circuit position and in phantom line inthe off or open position;

FIG. 2 is a fragmentary side elevational view to an enlarged scale of aportion of the mechanism of the center pole of the circuit breaker ofFIG. I with the parts shown in full line in the closed circuit or on"position and with certain of the parts shown in phantom line torepresent their position during circuit opening action; and

FIG. 3 is a fragmentary perspective view of the secondary armature andlatch assembly.

DETAILED DESCRIPTION OF THE ILLUSTRATED EMBODIMENT Turning now in detailto the attached drawing, therein illustrated is a three-pole circuitbreaker embodying the present invention and having a common insulatingcasing or housing generally designated by the numeral 10. Mounted withineach pole chamber of the casing are a pair of stationary contactassemblies l2, 14, one of which is connected to the line terminal 16 ofthat pole by conductor elements (not shown). The other of the contactassemblies l2, 14 is connected to the load terminal 30 of that polethrough the solenoid coil 32 thereof by conductor'elements (not shown).

Mounted for reciprocal movement within each pole chamber of the casing10 is an elongated contact operating rod 18 which carries at one end themovable wedgeshaped contact member 20 for movement into and fromelectrical contact with the stationary contact assemblies l2, l4 toprovide current flow therebetween. The contact operating rod 18 may bemoved from the open to the closed circuit position manually by operationof the manual operating handle mechanism 22 (only partially shown), themovement of which is translated to motion of the operating rod H8 byconventional toggle-type operating mechanism.

The operating mechanism of the center pole on'the illustrated embodimentincludes a releasable cradle 24 (only fragmentarily illustrated) whichhas a latch portion 26 at one end and which is supported for pivotalmovement upon a pivot (not shown) and held in latched position againstpivotal movement by the latch member 27 which is pivotably mounted onthe pivot 29. A pair of upper toggle links 28 (only one of which isshown) is positioned on opposite sides of the cradle 24 and is connectedthereto by a pivot pin (not shown). A pair of lower toggle links 34(only one of which is shown) is connected at its upper end to the uppertoggle links 28 by the pin 36. A pair of tension springs 44 (only one ofwhich is shown) connects the pin 36 to the manual operating handlemechanism 22.

This embodiment of the invention utilizes a multipole-type operatingmechanism of the type described and claimed in Johnson et al. US. Pat.No. 3,384,845 granted on May 21, I968 and assigned to the assignee ofthe present invention. Accordingly, the operating mechanism in each ofthe circuit breaker poles includes a pair of movable actuator plates 40(only one of which is shown in FIG. I and in FIG. 2), which arepivotably supported on the casing 10 by the pivot pin 42. In the centerpole. the lower ends of the lower toggle links 34 are connected by thepivot pin 38. The operation of the operating mechanism of the centralpole chamber of the three-pole breaker assembly serves to operate themovable contacts of all three poles by connection of the actuator plates40 in the center pole and corresponding actuator plates 40 in the outerpole chambers by means of the insulated tie bar 74 which extends throughapertures in the barrier sidewalls of the casing 10 between the centerand outer poles.

The contact operating rod 18 is bifurcated adjacent the movable contact20 and straddles a portion of the high speed connecting link or latch 46and is connected thereto by the pin 48 which extends through avertically elongated aperture 50 therein. The pin 52 is supported infixed position on the casing l0 and extends through arcuate slots 54 inthe contact actuator plates 40 and arcuate slot 56 in the latch 46. Theslots 54 and 56 are dimensioned and configured to provide clearance formovement of the pin 52 therein and to act as a stop or limit for theactuator plates 40 in the open and closed circuit positions thereof. Thelatch 46 is configured to provide a pair of vertically spaced,horizontally extending shoulder portions 58, 60 upon which rides theroller 62 which is carried by the shaft 64 seated in the actuator plates40.

The depending angular portion 66 on the latch 46 is engaged with an endof tension spring 68 which has its other end connected to the pin 70extending between the actuator plates 40. in this manner, the latch 46is biased counterclockwise about the pin 48 (as seen in FIG. 2) toretain the roller 62 upon the shoulder portion 60 of the latch 46 duringnormal operation.

Automatic operation of the contact operating rod 18 from closed to opencircuit position may be effected rapidly upon the occurrence of a highshort circuit current by means of magnetic action of the solenoid coil32 upon the primary armature or plunger 76 which is secured by thefastener 77 on the end thereof opposite that carrying the movablecontact 20.

As best seen in FIG. 2, the coil 32 is disposed about the tubular sleeve78 in which the primary armature 76 is slidable, and current flowingtherethrough generates a magnetic field acting upon the primary armature76. When a high short circuit current of predetermined magnitude passesthrough the solenoid coil 32, the magnetic force acting upon thearmature 76 is sufficient to draw the operating rod 18 from the fullline position shown in FIG. 2 to the phantom line position thereof, thuseffecting movement of the movable contact 20 from the contact assembliesl2, l4 and breaking the circuit. The action of the operating mechanismupon such movement of the operating rod 18 will be described in detailhereinafter.

According to the present invention, the contact operating rod 18 mayalso be moved from the closed to open circuit position by a lesser, butmore precisely predeterminable, short circuit current passing throughthe solenoid coil 32. A trip or secondary armature 80 is slidably.supported in the guide member 82 adjacent the solenoid coil 32 and issubject to the magnetic force generated by current flowing therethroughso as to be attracted thereto. Movement of the armature 80 away from thesolenoid coil 32 is limited by the collar 84 thereof which abuts theguide member 82.

As best seen in FIG. 3, a latch arm 86 is pivotably supported in thecasing 10 by the pivot pin 88 adjacent its upper end and it has ahook'shaped latch portion 90 which abuts the latch member 27 to preventits pivoting. At its lower end, the latch arm 86 is pivotably connectedto the armature 80 by the pivot pin 92. Attached to the lower end of thelatch arm 86 is one end of the tension spring 94 which has its other endconnected to the adjustment lever 96 which is pivotably supported on thecasing 10 by the pin 98.

The effective length of the spring 94 and thereby the biasing pressureduring normal operation can be varied by the trip adjustment screw 100which is threadably seated in an aperture 104 in the recess 106 of thecasing 10. As the screw 100 is turned inwardly of the casing 10, theadjustment lever 96 is pivoted counterclockwise as seen in FIGS. 1 and 2to elongate the spring 94 and thereby increase the biasing force actingupon the armature 80. Conversely. elevating the screw I00 allows theadjustment lever 96 to pivot clockwise under the action of the spring94'and thereby reduce the length and the biasing force.

MANUAL OPERATION OF THE BREAKER In the position shown in full line inFIGS. I and 2. the movable contact is in engagement with and completesthe circuit between the contact assemblies 12, I4. The action of thetoggle springs 44 and of the spring 68 biases the movable contact intothe closed circuit position. In the closed circuit or "on" position, theline of action of the toggle springs 44 is to the left of the pivot (notshown) between the upper toggle links 28 and the releasable cradle 24.When the operating handle assembly 22 is moved from the "on" position tothe off" position, the line of action of the toggle springs 44 moves tothe right of the pivot (not shown) between the upper toggle links 28 andreleasable cradle 24, thus causing the toggle linkage to buckle to theright and the parts to move to a manuallyactuated off" position (notshown) wherein the movable contact 20 is moved to the phantom lineposition shown in FIG. 2. In this manual operation, the contact actuatorplates 40 are rotated clockwise about the pivot pin 42 by reason oftheir connection to the lower toggle links 34 through the pin 38. P Asthe actuator plates 40 pivot, the roller 62 is engaged by the hookportion of the latch 46 and the latch 46 is moved to the right as seenin FIG. 2, thereby moving the contact operating rod 18 to the "off"position as a result of the engagement provided by the pin 48.

Movement of the operating mechanism of the illustrated center pole tothe off" position will simultaneously produce movement of the operatingmechanism of the other poles of the breaker assembly to the off"position since the contact actuator plates 40 thereof are rigidly tiedtogether by the tie bar 74 extending therebetween. The pivoting of thecontact actuator plates 40 in the other pole chambers in the clockwisedirection will cause the contact operating rods 18 therein to move toopen circuit position.

OPERATION OF THE BREAKER MECHANISM UPON OCCURRENCE OF A HIGH SHORTCIRCUIT CURRENT As previously indicated, the current flowing through thesolenoid coil 32 produces a magnetic force acting upon the primaryannature 76 which is carried by the contact operating rod 18. When theshort circuit current in any one of the circuit breaker poles reaches apredetermined value, the magnetic force generated by the solenoid coil32 is sufficient to draw the primary armature 76 thereto at high speedand to open the circuit through movement of the contact operating rod I8and the movable contact 20 away from the stationary contact assemblies12, I4. The motion of the contact operating rod 18 is transmitted to thelatch 46 by reason of the engagement of the pin 48 therewith. As will beappreciated, the latch '46 rotates in a clockwise position about the pin52 against the biasing action of the spring 68, thus moving the shoulder60 below the level of the roller 62. As the roller 62 clears theshoulder 60, the latch 46 slides to the right under the influence of thespring 68 and the magnetic force of the solenoid coil 32 acting upon thearmature 76. The roller 62 then seats against the shoulder 58 of thelatch 40. In this manner, the operating rod I8 is moved rapidly bymagnetic action with minimum inertial resistance of the operatingmechanism, thus effecting high speed opening.

As will be readily appreciated, a short circuit current of suf-- ficientmagnitude to draw the primary armature 76 to the solenoid 32 and openthe contact will also draw the secondary armature 80 towards thesolenoid coil 32. This movement will effect pivoting of the latch arm 86in the center pole and release of the latch member 27 so that thebiasing pressure of the automatic operating mechanism therein will pivotthe eradie 24, collapsing the toggle mechanism and causing pivoting ofthe contact actuator plates 40 in the center pole chamber and therebythe contact actuator plates 40 in each ofthe outer poles since they areconnected together by the tie bar 74. As a result, the contact operatingrod ltl in each of the poles is moved to open circuit position. If theshort circuit current occurs in either of the outer pole chambers, themovement of the secondary armature 80 therein actuates the mechanism ofthe center pole chamber by relatively simple tie structure which is notillustrated. The secondary armatures in the outer pole chambers eachhave a trip member (not shown) extending upwardly therefrom which willstrike against and pivot a depending arm (not shown) carried by thecommon pivot pin or shaft 88 which extends through all three poles. As aresult, the latch arm 86 in the center pole is pivoted by movement ofthe secondary armatures 80 in either of the outer poles and theoperating mechanism of the center pole will cause pivoting of thecontact actuator plates 40 therein and thereby. the pivoting of thecontact actuator plates 40 in the remaining outer pole.

Thus, high speed opening of the circuit breaker under the solenoidaction in any of the pole chambers will effect opening of the contactsin the other pole chambers. In addition, the operating mechanism will betripped to the trip indicating position, and the operating mechanism maybe reengaged with the operating rod 18 for reclosing of the circuit.

OPERATION OF THE BREAKER MECHANISM UPON OCCURRENCE OF A SHORT CIRCUITCURRENT O LESSER MAGNITUDE As willbe appreciated. the adjustmentmechanism for the tension spring 94 acting upon the secondary armature80 may be relatively closely adjusted to permit operation of the breakermechanism upon the occurrence of a short circuit current oflessermagnitude than that required to effect movement of the contact operatingrod I8 independently of the operating mechanism. If the short circuitcurrent flowing through the solenoid coil 32 exceeds the calibratedvalue established by the adjustment of the tension spring 94, thesecondary armature 80 will be drawn towards the solenoid coil 32 toeffect circuitopening action.

In the center pole of the illustrated breaker assembly which containsthe automatic operating mechanism, this movement of the armature 80 willpivot the latch arm 86 in a clockwise direction and release the latchmember 27 so that it may pivot in a clockwise direction under thebiasing pressure of the toggle springs 44. As a result, the cradle 24will pivot and the toggle linkage will produce pivoting of the contactactuator plates 40 about their pivot pin 42 in a clockwise directionwith resultant movement of the contact operating rod I8 to the opencircuit position. As the contact actuator plates 40 of the center polepivot, the contact actuator plates 40 of the other poles simultaneouslypivot because of the connection of the tie bar 74 therebetween, thuseffecting opening of the contacts in the outer poles.

In the multipole embodiment of the present invention illustrated.magnetic movement of the secondary armature 80 in either of the outerpole chambers will effect pivoting of the latch arm 86 on the commonpivot pin or shaft 88 as hereinbefore described. In this manner, theoperating mechanism of the center pole will be tripped and the contactswill be opened in both the center pole chamber and the remaining outerpole chamber.

The movement of the secondary armature 80 inwardly of the solenoid coil32 will also tend to increase the magnetic force acting upon the primaryarmature 76. The resultant increased magnetic force may be sufficient todraw the primary armature 76 to the solenoid coil 32 for high speedmagnetic action independently of the automatic operating togglemechanism which is slower in action.

Although the present invention has been illustrated and described withrespect to a multipole breaker, it will be readily appreciated that itis particularly adapted to single pole breaker operation. Moreover, inmultipole breaker constructions, each of the several poles may includeautomatic operating mechanism such as that illustrated herein for thecenter pole chamber.

As will be appreciated, various means may be used to provide thereleasable interconnection between the automatic operating mechanism andthe contact operating member so long as the connection may be overriddenor released upon development ofa magnetic force of predeterminedmagnitude as a result of a short circuit. Highly advantageous mechanismsare that illustrated herein and those described in the afore mentionedGiger U.S. Pat. No. 3.495.198 and Hurtle U.S. Pat. No. 3,483,490.

Similarly, various other manual and automatic operating mechanisms maybe employed in accordance with the present invention such as, forexample. the manual operating mechanism shown in the aforementionedHurtle U.S. Pat. No. 3,483,490. When the present invention is utilizedin multipole breakers, the interconnection of the several poles may bethrough the common pivot for the latch as in the illustrated embodimentor other means may be employed such as a sliding rod extending betweenthe secondary armatures through the barrier walls. Other techniques foreffecting concurrent operation of the several poles are well known andunderstood and will be apparent to those having ordinary skill in theart.

In the present invention, the biasing pressure of the spring againstwhich the secondary armature must be moved by the magnetic force of thesolenoid coil is varied by pivotal action of the adjustment lever. Othermeans for varying the length and thereby the tension of such a springmay be employed such as a slide connection extending through the casing,a threaded fastener engaged directly therewith and movable relative tothe wall of the casing, etc. In place of an intermediate latch armacting upon the latch for the cradle, the latch itself may be ofsufficient length so as to be engaged with the secondary armature or aflag on the secondary armature may strike a depending portion on thelatch to effect pivotal movement thereof.

If so desired, the circuit breaker may also include conventional thermaltrip mechanism such as the bimetal strip-type wherein a short circuit oflow magnitude extending over a sufficient period of time will producerelease of the latch mechanism of the automatic operating mechanism foropening of the contacts. Such devices may employ various means foreffecting the releasing action such as by having the bimetallic stripact upon the secondary armature to produce movement thereof towards thesolenoid coil or by having it act upon the latch member directly or anelement engaged therewith.

Thus, it can be seen from the foregoing detailed specification anddrawing that the present invention provides a highly effective electriccircuit interrupter which is capable of rapidly opening the contactstherein independently of the manual operating mechanism whileconcurrently effecting movement of the operating mechanism to thetripped condition. The circuit interrupters of the present invention maybe simply and economically constructed and the magnitude of the shortcircuit current required for tripping of the breaker may bepredetermined with a high degree of accuracy.

What I claim as new and desire to secure by Letters Patent of the UnitedStates is:

Iclaim:

1. In an electric circuit interrupter, the combination comprising:

a. a casing;

b. at least one stationary contact in said casing;

c. a movable contact;

d. a contact operating member carrying said movable contact adjacent oneend thereof;

e. means mounting said contact operating member for movement of saidmovable contact into and from contact with said stationary contactbetween closed and open circuit positions;

f. operating means connected to said operating member for automaticallymoving said contact operating member from closed to open circuitposition;

g. releasable means latching said operating means against said automaticmovement;

h. a first armature on said contact operating member adjacent the otherend thereof;

i. a solenoid having one end thereof adjacent said first armature. saidsolenoid generating a magnetic force acting upon said first armaturesufficient to draw said contact operating member into open circuitposition upon passage of a short circuit current of predeterminedmagnitude therethrough;

j. a second armature adjacent the other end of said solenoid andattractable thereby; and

k. means mounting said second armature in said casing for movement froma normal position towards said solenoid into a circuit opening positionupon passage through said solenoid of a short circuit current ofpredetermined magnitude, said second armature acting to cause movementof said latching means upon movement of said second armature toward saidcircuit opening position to release said operating means for automaticoperation thereof.

2. The circuit interrupter of claim 1 wherein there is includedadjustable biasing meansengaged with said second armature and biasingsaid second armature into said normal position, said biasing means beingadjustable to vary the magnetic force required to attract said secondarmature into circuit opening position.

3. The circuit interrupter of claim 2 wherein sad adjustable biasingmeans includes an adjustment lever pivotably mounted within said casing,tension spring means connected between said second armature and saidadjustment lever, and adjustable means for pivoting said adjustmentlever to vary the length of said tension spring means and thereby thebiasing pressure exerted thereby upon said second armature.

4. The circuit interrupter of claim 1 wherein there is included anintermediate latching member cooperating with said latching means andoperable upon movement of said second armature to release saidreleasable means for automatic operation of said operating means.

5. The circuit interrupter of claim 4 wherein said intermediate latchingmember is a latch arm pivotably mounted in said casing at one end andpivotably connected to said second armature at its other end, said latcharm being engaged with said releasable latching means for said operating means in the normal position of said armature, said latch armreleasing said latching means upon movement of said second armature tosaid circuit opening position to cause said automatic operation of saidoperating means.

6. The circuit interrupter of claim 5 wherein said releasable meanslatching said operating means is a pivoted latch held in latchedposition by engagement with a portion of said intermediate latchingmember in the normal position of said armature.

7. The circuit interrupter of claim I wherein there is includedadjustable biasing means engaged with said second armature and biasingsaid second armature into said normal position, said biasing means beingadjustable to vary the magnetic force required to attract said armatureinto circuit opening position; and wherein there is also included anintermediate latching member. cooperating with said latching means andoperable upon movement of said second armature to release saidreleasable means for automatic operation of said operating means.

8. The circuit interrupter of claim I wherein said mounting means forsaid second armature includes a guide member in said'casing in whichsaid second armature is slidably seated.

9. The circuit interrupter of claim 1 wherein said operating meansincludes a pivotable cradle. a toggle mechanism biasing said cradle forpivotal movement upon release of said releasable means. and releasablemeans connecting said toggle mechanism to said contact operating memberfor movement thereof into open circuit position upon pivoting of saidcradle.

[0. The circuit interrupter of claim 9 wherein said connecting means isreleasable upon operation of said first armature by said solenoid topermit movement of said contact operating member to open circuitposition independently of the operating means.

II. The circuit interrupter ot'claim 9 wherein said connecting means maybe overridden upon operation of said first armature by said solenoid topermit movement of said contact operating member to open circuitindependently of the operating means 1 12. In an electric circuitinterrupter, the combination com prising:

a. a casing;

b. at least one stationary contact in said casing;

c. a movable contact;

d. a contact operating member carrying said movable contact adjacent oneend thereof;

e. means mounting said contact operating member for movement of saidmovable contact into and from contact with said stationary contactbetween closed and open circuit positions; operating means connected tosaid operating member for automatically moving said contact operatingmember from closed to open circuit position; said operating meansincluding a pivotable cradle. a toggle mechanism biasing said cradle forpivotal movement. and releasable means connecting said toggle mechanismto said contact operating member;

g. releasable means latching said operating means against said automaticmovement;

h. a first armature on said contact operating member adjacent the otherend thereof;

i. a solenoid having one end thereof adjacent said first armature, saidsolenoid generating a magnetic force acting upon said first armaturesufficient to draw said contact operating member into open circuitposition upon passage of a short circuit current of predeterminedmagnitude therethrough;

j. a second armature adjacent the other end of said solenoid andattractable thereby;

k. means mounting said second armature in said casing for movement froma normal position towards said solenoid into a circuit opening positionupon passage through said solenoid of a short circuit current ofpredetermined magnitude;

l. adjustable biasing means engaged with said second armature andbiasing said second armature into said normal position, said biasingmeans being adjustable to vary the magnetic force required to attractsaid second armature into circuit opening position; and

m. an intermediate latching member cooperating said latching means andoperable upon movement of said second armature to release saidreleasable means for automatic operation of said operating means, saidreleasable connecting means between said toggle mechanism and saidcontact operating member permitting movement of said contact operatingmember into open circuit position upon pivoting of said cradle, saidconnecting means being releasable upon operation of said first armatureby said solenoid coil to permit movement of said contact operating rodto open circuit position independently of the operating means.

13. The circuit interrupter ofclaim 12 wherein said adjustable biasingmeans includes an adjustment lever pivotably mounted within said casing,tension spring means connected between said second armature and saidadjustment lever, and adjustable means for pivoting said adjustmentlever to vary the length of said tension spring means and thereby thebiasing pressure exerted thereby upon said second armature.

14. The circuit interrupter of claim 12 wherein said intermediatelatching member is a latch arm pivotably mounted in said casing at oneend and pivotably connected to said second armature at its other end,said latch arm being engaged with said releasable latching means forsaid operating means in the normal position of said armature, said latcharm releasing said latching means upon movement of said second armatureto said circuit opening position to cause said automatic operation ofsaid operating means.

